This invention relates to flexible hoses having a soft hose main body and helical rigid reinforcing means embedded partially or wholly in the wall of the main body.
With flexible hoses of this type, the helical pitch and cross sectional area of the helical rigid reinforcing means closely relate to the flexibility of the hose and its strength against flattening and against pressure. The larger the helical pitch of the reinforcing means, the larger is the width of the soft wall portion between the adjacent coils of the reinforcing means in the axial direction of the hose and the higher will be the flexibility of the hose, whereas the strength against flattening and the pressure resistant strength decrease with an increase in the helical pitch. Accordingly, the alterations of the helical pitch give a conflicting relation between the flexibility and the strength against flattening and pressure. Further as the cross sectional area of the reinforcing means increases, the reinforcing means has increasing bending strength, imparting to the hose enhanced strength against flattening but reduced flexibility. Variations in the cross sectional area of the reinforcing means therefore similarly give a contradictory relation between the flexibility and the strength against flattening and pressure.
Thus, the flexibility, strength against flattening and strength against pressure of the hose depend heavily on the helical pitch and cross sectional area of the reinforcing means.
In view of these characteristics, the flexible hoses of this invention have been developed.